Module planner 

Query Planner - Integrates statistics and cost-based optimization

This module provides the QueryPlanner which coordinates between:

• Table statistics stored in system tables (sys_table_stats, sys_column_stats)
• Cost estimator for choosing access methods
• Zone maps for segment pruning
• Index selection for efficient access paths

The planner is used by the executor to make informed decisions about:

• Whether to use an index vs sequential scan
• Which join algorithm to use
• Which segments can be skipped using zone maps

Re-exports

pub use crate::join_executor::RuntimeJoinAlgorithm;

pub use crate::join_executor::RuntimeJoinDecision;

Structs

ColumnStatsCache

Cached column stats (simplified for internal use)

QueryPlanner

Query planner that integrates statistics-based optimization

Enums

StatsHealth

Health status of table statistics